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Modelling of the Fletcher-Gent effect and obtaining hyperelastic parameters for filled elastomers
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.ORCID iD: 0000-0002-1036-6837
2014 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The strain amplitude dependency , i.e. the Fletcher-Gent effect and Payne effect, and the strain rate dependency of rubber with reinforcing fillers is modelled using a modified boundary surface model and implemented uniaxially. In this thesis, a split of strain instead of stress is utilized, and the storage and loss modulus are captured over two decades of both strain amplitudes and frequencies. In addition, experimental results from bimodal excitation are replicated well, even though material parameters were obtained solely from harmonic excitation. These results are encouraging since the superposition principle is not valid for filled rubber, and real-life operational conditions in general contain several harmonics. This means that formulating constitutive equations in the frequency domain is a cumbersome task, and therefore the derived model is implemented in the time domain. Filled rubber is used irreplaceable in several engineering solutions, such as tires, bushings, vibrations isolators, seals and tread belts, to name just a few. In certain applications, it is sufficient to model the elastic properties of a component during finite strains. However, Hooke’s law is inadequate for this task. Instead, hyperelastic material models are used. Finally, the thesis presents a methodology for obtaining the required material parameters utilizing experiments in pure shear, uniaxial tension and the inflation of a rubber membrane. It is argued that the unloading curve rather than the loading curve is more suitable for obtaining these parameters, even at very low strain rates.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. , x, 54 p.
Series
TRITA-AVE, ISSN 1651-7660 ; 2014:47
Keyword [en]
filled elastomers, natural rubber, carbon black, Fletcher-Gent effect, Payne-effect, finite strain, hyperelastic
National Category
Other Natural Sciences
Identifiers
URN: urn:nbn:se:kth:diva-151304ISBN: 978-91-7595-273-4 (print)OAI: oai:DiVA.org:kth-151304DiVA: diva2:747655
Presentation
2014-10-08, Munin, Teknikringen 8, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20140917

Available from: 2014-09-17 Created: 2014-09-17 Last updated: 2014-09-24Bibliographically approved
List of papers
1. Constitutive modelling of the amplitude and frequency dependency of filled elastomers utilizing a modified Boundary Surface Model
Open this publication in new window or tab >>Constitutive modelling of the amplitude and frequency dependency of filled elastomers utilizing a modified Boundary Surface Model
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2014 (English)In: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 51, no 19-20, 3431-3438 p.Article in journal (Refereed) Published
Abstract [en]

A phenomenological uniaxial model is derived for implementation in the time domain, which captures the amplitude and frequency dependency of filled elastomers. Motivated by the experimental observation that the frequency dependency is stronger for smaller strain amplitudes than for large ones, a novel material model is presented. It utilizes a split of deformation between a generalized Maxwell chain in series with a bounding surface plasticity model with a vanishing elastic region. Many attempts to capture the behaviour of filled elastomers are found in the literature, which often utilize an additive split between an elastic and a history dependent element, in parallel. Even though some models capture the storage and loss modulus during sinusoidal excitations, they often fail to do so for more complex load histories. Simulations with the derived model are compared to measurements in simple shear on a compound of carbon black filled natural rubber used in driveline isolators in the heavy truck industry. The storage and loss modulus from simulations agree very well with measurements, using only 7 material parameters to capture 2 decades of strain (0.5-50% shear strain) and frequency (0.2-20 Hz). More importantly, with material parameters extracted from the measured storage and loss modulus, measurements of a dual sine excitation are well replicated. This enables realistic operating conditions to be simulated early in the development process, before an actual prototype is available for testing, since the loads in real life operating conditions frequently are a combination of many harmonics.

Keyword
Amplitude dependency, Boundary Surface Model, Carbon black, Filled elastomers, Fletcher-Gent Effect, Natural rubber
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-151310 (URN)10.1016/j.ijsolstr.2014.06.003 (DOI)000341469900012 ()2-s2.0-84906245570 (Scopus ID)
Note

QC 20140917

Available from: 2014-09-17 Created: 2014-09-17 Last updated: 2017-12-05Bibliographically approved
2. An efficient method for obtaining the hyperelastic properties of filled elastomers in finite strain applications
Open this publication in new window or tab >>An efficient method for obtaining the hyperelastic properties of filled elastomers in finite strain applications
2015 (English)In: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 41, 44-54 p.Article in journal (Refereed) Published
Abstract [en]

An efficient methodology for obtaining hyperelastic material parameters for filled elastomers utilizing unloading curves in uniaxial tension, pure shear and the inflation of a rubber membrane is presented. Experimental results from biaxial extension are crucial when fitting hyperelastic material parameters, and the bubble inflation technique is an excellent method of obtaining this data when specialized test equipment is unavailable. Moreover, filled elastomers have considerable hysteresis, and the hysteresis grows with increasing strain amplitudes. Therefore, the loading curve is in general comprised of both elastic and inelastic contributions, even at very low strain rates. Consequently, it is deemed more accurate to use experimental data from the unloading curve to describe the elastic behavior of the material. The presented methodology enables obtainment of parameters related to both the first and second strain invariant, which is required for a good fit between measurement and simulation results. Finally, it is essential that a chosen material model is accurate in all deformation modes when designing components subjected to a complex, multi-axial load history. An accurate material model enables more concepts and geometries of a component to be studied before a physical prototype is available.

Keyword
Filled elastomers, Hyperelasticity, Material parameters
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-151311 (URN)10.1016/j.polymertesting.2014.10.008 (DOI)000348970100008 ()2-s2.0-84909608138 (Scopus ID)
Note

QC 20140917. QC 20150316. Updated from manuscript to article in journal.

Available from: 2014-09-17 Created: 2014-09-17 Last updated: 2017-12-05Bibliographically approved

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